An Efficient Approach to Heterocyclic Analogues of Xanthone: A Short Synthesis of All Possible Pyrido[5,6]pyrano[2,3-<i>c</i>]pyrazol-4(1<i>H</i>)-ones
作者:Gernot Eller、Wolfgang Holzer、Veronika Wimmer、Andreas Haring
DOI:10.1055/s-2006-950324
日期:——
An efficient and generally applicable synthesis of various [5,6]pyrano[2,3-c]pyrazol-4(1H)-ones by the reaction of either 1-substituted or 1,3-disubstituted 2-pyrazolin-5-ones with different o-halopyridinecarbonyl chlorides or with 3-chloroquinoline-2-carbonyl chloride, using calcium hydroxide in 1,4-dioxane, is described. In the course of the preparation of pyrazolo[4′,3′:5,6]pyrano[2,3-c]pyridin-4(1H)-ones, the intermediate 4-(3-chloroisonicotinoyl)-1H-pyrazol-5-ols did not cyclize spontaneously and thus were transformed into the corresponding tricycles by treatment with NaH in DMF. The N1-unsubstituted title compounds were obtained upon treatment of the corresponding 1-(4-methoxybenzyl) protected congeners with trifluoroacetic acid.
描述了一种高效且普遍适用的合成不同 [5,6]吡喃[2,3-c]吡唑-4(1H)-酮的方法,包括将1-取代或1,3-二取代的2-吡唑啉-5-酮与不同的卤代吡啶酰氯或与3-氯喹啉-2-酰氯反应,使用氢氧化钙和1,4-二噁烷。在合成吡唑[4′,3′:5,6]吡喃[2,3-c]吡啶-4(1H)-酮的过程中,中间体4-(3-氯异尼古丁酰)-1H-吡唑-5-醇未能自发环化,因此通过在DMF中用氢化钠处理,转化为相应的三环化合物。在用三氟醋酸处理相应的1-(4-甲氧基苄基)保护同系物后,得到了N1未取代的目标化合物。